Answer:
7
Explanation:
4f corresponds to quantum numbers n=4 and l=3.
the values of ml depends of l in the form:
[tex]m_l=-l,...,0,...,+l[/tex]
Hence, by replacing we obtain:
[tex]m_l=-3,-2,-1,0,1,2,3[/tex]
Thus, there are 7 sublevels
hope this helps!!